For the fabrication of semiconductor devices, a wafer undergoes a variety of processes. Among these processes, a photolithography process is used to form a pattern on the wafer, and it includes a coating process of coating a photosensitive solution, such as a photoresist on the wafer, a photographing process of irradiating light onto the coated photoresist to form a provisional image for the pattern to be formed, and a developing process of developing the provisional image into the pattern. In the coating process, it is very important to coat the photoresist in a uniform thickness and at a set thickness, and the temperature of the wafer has a large influence on the thickness uniformity of the photoresist coated thereon.
Before the coating process is performed, the wafer is generally heated or cooled in a bake module, and then transferred by a robot to a module to perform the coating process. The temperature of the wafer is influenced by a contact with the robot. As such, in order to maintain the wafer at the process temperature, a temperature control member controlling the temperature of the wafer is provided in the robot.
In general, two or more bake modules are provided in up/down direction or left/right direction in a substrate treating apparatus. The contact time of wafers with the transfer robot is varied depending on the position of the bake modules in which processes are performed. Accordingly, it is not easy to control the temperature of the wafers equally and precisely. Also, since only a selected region of the wafer contacts the robot, the temperature of the wafer is different according to its regions.
The aforementioned drawback causes the photoresist to be coated in a coating process with a low uniformity between wafers or between regions in a single wafer.